In the related art, a solid state drive (SSD) (hereinafter, referred to as storage device) that has an authentication function and uses a NAND memory that is a nonvolatile semiconductor memory receives a data access request from a host device and outputs user data recorded in an area designated from the host device, when authentication of a password of a user who has access authority is succeeded. When the storage device has an encryption function, if the authentication of the password is succeeded, the storage device sets a previously stored encryption key as a decryption key and outputs user data obtained by decrypting encrypted user data by the decryption key. As such, the storage device according to the related art can output correct user data to the user who has access authority.